Bituminous mastics products



IMPROVED BITUMINOUS MASTIC CONTAINING FILLER AND FIBRE.

IMPRESSED GRANULES OR MINERAL DUsT. IMPROVED BITUMINOUS MAsTIc.

IMPROVED BITUMINOUS MASTIC.

W- F. FAIR, JR

BITUMINOUS MASTICS PRODUCTS Filed April 24, 1951 Feb. 1, 1955 GRANULES0R MINERAL DUST.

DIR-GOAT.

IMPROVED BITUMINOUS MASTIC.

DIP-COAT.

IMPROVED DITUNIINoUs MASTIC CONTAINING FILLER AND FIBER.

- IMPREssED'GRANULEs OR MINERAL DUST.

IMPROVED BITUMINOUS MASTIC.

IMPRESSED GRANULES OR MINERAL DUST. v

IMPROVED BITUMINOUS -DIPCOATING.

M ASTI C INVENTOR: flaw WM 4* WW ATTORNEY United States PatentBITUMINOUS MASTICS PRODUCTS William F. Fair, J12, Cranford, N. J.,assignor to Koppers Company, Inc, a corporation of Delaware ApplicationApril 24, 1951, Serial No. 222,639

7 Claims. (Cl. 117-168) The present invention relates to improvements inbituminous mastic sheet material and methods of preparing such material.

Bituminous mastics have been widely used for various purposes ascements, as coatings for surfaces, as flooring, and on walls. They havegenerally been applied by brushing, or trowelling and rolling, or in theform of solid blocks or cakes. Little success has been realizedcommercially in the past in providing a coherent, fiexible,self-sustaining, prefabricated, non-reenforced type of bituminous masticsheet that can be sold and handled as such, as distinct from saturatedfelt sheets or sheets containing reenforcing webs or inserts.Conventional bituminous mastic was considered objectionable forprefabricated sheeting for various reasons and mainly because it becometoo brittle in cold weather or was subject to fusion and flow in hotweather.

The present invention overcomes the objections raised with respect topreviously known bituminous mastic sheets by providing a prefabricatedbituminous mastic sheet that is pliable at low atmospheric temperaturesand that shows no tendency to flow at high atmospheric temperatures, andthat retains its flexible, solid-sheet form. The sheet is for widecommercial application in view of its high insulation value, fireresistance, resistance to weathering, inertness to the action of waterand ultraviolet light, resistance to flow, and its non-cracking andnon-shattering characteristics. By treatments described below, thesedesirable properties are also effectively imparted to bituminous masticsheets or to conventional tar, pitch and asphalt mastics, rendering themmore highly useful in structures such as roofing including shingles,rolls, sidings, panels, insulation, subflooring, ex pansion joints, andother articles.

In the preparation of the improved mastic sheet, the materials employedinclude coal-digestion pitch, a finely divided filler, and discretefiber particles. Coal-digestion pitch comprises coal dispersed bydigestion in a heatliquefiable bituminous medium. The medium containsheavy hydrocarbon oil; or heavy hydrocarbon oil containing apreponderating proportion of aromatic hydrocarbons or constituents isadded during or preferably after the digestion and dispersion process,or during or preferably after thermal treatment of coal by such process.

In the accompanying drawings, Figs. 1 to 7 are diagrammaticillustrations, in vertical section, of fragments of sheets made inaccordance with the present invention.

A sheet, in fiat form 1 (Figs. 1 to 4) or in corrugated form 2 (Figs.and 6), is prepared from a mixture, more particularly describedhereinbelow, which is shaped by rolling, extrusion, or by compression ina mold. The improved bituminous mastic, because of its composition,lends itself well to shaping into sheets by any suitable mechanicalmeans. To provide for additional surface protection, granules or ductsof solid, inert, oil and waterinsoluble, heat-resistant mineral, ormetallic, or artificial pigment material, are distributed on the surfaceof a sheet. Colored granules or dusts are employed for producing variouscolor schemes. The granules or dust particles are anchored as at 3 (Fig.2) on one side of a sheet, or as at 4 and 5 (Fig. 6) on both sides of asheet by impressing them into the surface, or they are bonded to thesurface by means of a bituminous cement or a dip-coat of coal-digestionpitch, as described below, and as shown at 6 (Fig. 4).

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Suitable coatings applied by brushing or spraying, or preferably adip-coat, as shown at 7 (Fig. 3), are provided for various purposes, ifdesired.

In preparing the coal-digestion pitch, coal, such as bituminous coals orcoking coals including either highor low-volatile bituminous coal, andcertain commercial non-coking bituminous coals, is heated while admixedwith tar or pitch. The temperature of the mixture while stirring thelatter, is gradually increased over an extended period of time tosubstantially 300 C. or preferably to a temperature in the approximaterange of 300 C. to 310 C. The temperature employed is generally notlower than about 270 C. nor higher than about 350 C. The coal isuniformly distributed in the course of the thermal digestion and mixingprocess and, in effect, constituents of the coal at the temperatureemployed appear to undergo a dissolution in the tar or pitch. Dependingon the temperature and the time of digestion, it has in certaininstances been impossible to determine whether a chemical change hasoccurred in the coal, and in other instances such change has been moreor less definitely detectable. For purposes of the present invention,control tests comprising softening point and penetration determinationsare employed to provide a sheet with pitch having the designatedimproved characteristics resulting from a digestion and blendingprocess.

To obtain a pitch of highly desirable characteristics for the purposesof the present invention, either before but preferably after dispersionof coal in the tar and/or pitch in the digestion process, there is addedthe abovementioned heavy hydrocarbon oil. The heavy hydrocarbon oil is ahigh-boiling distillate obtained by distilling tar and separating thedistillate recoverable above approximately 300 C. Only a minorproportion (about 15 per cent or less) of the oil boils below 300 C. Theboiling points may be within the approximate range of 250 C. to 450 C.

Heavy hydrocarbon oils that have been employed are such oils as heavywater gas tar heavy oil, light water gas tar heavy oil; and coal tarheavy oils from tars known as low temperature coal tar and hightemperature coal tar.

Heavy water gas tar heavy oils, used advantageously in the mastic, aresubstantially aromatic in character, and are obtained by distillationfrom heavy water gas tar which in turn is obtained from water-gasgenerator plants in which Bunker-C or similar grades of residualpetroleum fuel oil are used for carburetting. Heavy water gas tar isalso known as residuum tar and is thus termed to distinguish it fromwhat was formerly known as water gas tar or is known today specificallyas light water gas tar. Light water gas tar heavy oil is obtained fromlight water gas tar which is produced in the carburettor of a water gasplant when petroleum distillates are used as carburetting agents.

Depending upon the proportions of coal, tar and/or pitch, and/or heavyoil, in the coal-digestion pitches, or on the proportion of such oiladded to these pitches the resulting pitch products have been preparedwith ring and ball softening points in the approximate range of 35 C. toC., all exhibiting improved rheological properties, as well asconsiderably better temperature susceptibilities (that is, less changein viscosity with temperature change) and greater resistance to flowthan the commonly used bitumens, when in layers or on surfaces invertical position as well as in inclined position.

The following, by way of illustration, are examples of coal-digestionpitch that is employed in the present invention:

A. About 187 parts by weight of heavy water gas tar and about 47 partsby weight of powdered bituminous coal are heated together in a stillpreferably while stirring. The temperature is gradually raised to atemperature of about 305 C. over a period of approximately five andone-half hours. This temperature is maintained for about four hoursduring which time there results a distillate of about 5 to 6% based onthe tar. At the end of this time heating is discontinued and the mixturepermitted to cool. After about forty minutes and while the temperatureis slowly dropping, about 54 parts by weight of heavy water gas tarheavy oil are stirred into the heat-treated coal and tar mass. Theresulting product is discharged from the still at around 225 C. Thesoftening point of this product is about 102 C., and the penetration at32 F. is 14; at 77 F. is 20.5; and at 115 F. is 4-0.

B. A mixture prepared from approximately 174 parts by weight of cokeoven tar and approximately 53 parts by weight of pulverized bituminouscoal is heated to about 300 C. over a period of seven to eight hours.The heating is discontinued and about 72 parts by weight of heavy watergas tar heavy oil are added whereupon the heating is resumed at about300 C. for an additional one to two hours. Then another 15 parts byweight of heavy Water gas tar heavy oil are added whereafter the heatingis discontinued and after thorough mixing the product is permitted tocool. The softening point of the product is about 89 C. and thepenetration at 32 F. is 24; at 77 F. is 38; and at 115 F. is 67.

In either Examples A or B, the heavy water gas tar heavy oil may besubstituted by light water gas tar heavy oil provided high melting cokeoven pitch is included in the composition; though the heavy water gastar heavy oil alone is preferred.

C. A still is charged with 310 parts by weight of crude light water gastar and 40 parts of light water gas tar heavy oil. To this mixture 40parts of molten high melting coke oven pitch having a melting point of145 C. (cube in air), and 72 parts of pulverized coal are added. Thismixture is heated to 300 C. in approximately one hour and maintained atabout 300 C. for approximately three hours with agitation, 23 parts ofdistillate being removed. The residual pitch has a softening point of 88C (ring and ball) and penetrations at 32 F. (200 grams, 60 seconds) of20, at 77 F. (100 grams, 5 seconds) of 32 and at 115 F. (50 grams, 5seconds) of 61.

D. A mixture of 39.5% by weight of residuum tar, 37.4% by weight ofcoal-tar heavy oil, and 23.1% by weight of pulverized bituminous coal issubjected to a digestion temperature of about 315 C. to obtain acoaldigestion pitch with an R. and B. softening point of 109 C., apenetration at 32 F. of 12, a penetration at 77 F. of 22, and apenetration at 115 F. of 50.

In some cases, one to two parts by weight of sulfur may be included inthe coal-digestion mixture, or air may be introduced for varyingperiods. The air and sulfur serve as dchydrogenating agents by whichwith subsequent addition of heavy oil, the characteristics of the pitchmay alternatively be adjusted.

The filters employed in the mastic may be sand, clay, slate dust and thelike or mixtures thereof. The fibers may be mineral, vegetable or animalfibers or mixtures thereof including asbestos. cotton (such as thatreclaimed from tires), hair and so forth. As previously indicated, it ispreferable, particularly if the mastic is not subsequently dip-coated,to precoat the fibers. For this purpose there are employed tars such ascoal tars including coke oven tar, horizontal retort tar, and verticalretort tar; heavy water gas tar and light water gas tar; oil-gas tar,Pintsch gas tar; wood tar; pitches of such tars; oils from such tars;asphalt; mixtures of these bituminous substances; or coal-digestionpitches either molten or dispersed in volatile solvent. If desired, anywater repellent material may be used to precoat the fibers but it shouldpreferably be miscible or compatible with the bituminous material in themastic. For instance, a non-aromatic petroleum distillate should not beused to precoat the fibers, if a tar-derived composition is to be usedin the mastic.

The precoating of the fibers is preferably accomplished in a Banburymixer, though this is also done by dipcoating and then centrifuging toremove the excess coating material. In a Banbury mixer, about parts byweight of coal-digestion pitch, such as exemplified above,satisfactorily coats about 85 parts by weight of fiber.

A rubber roll mill, pug mill, or a Banbury mixer may be used to preparethe mastic. The fillers and bituminous material used in the mastic arefirst mixed together and then the fibers, either precoated or untreatedare added and mixed with the first two ingredients. When using a rubberroll mill, the bituminous material is melted on the heated rolls andthen the filler and fibers are successively added and mixed. When usinga pug mill, the melted bituminous material and filler are mixed in themill, and the fibers are mixed with the resulting mixture in a pug mill,a rubber mill or in a Banbury mixer.

The proportions of constituents employed in the mastic may vary widely.Too much of the bituminous material of a low softening point should notbe used if the mastic is to be pliable and yet retain itspressure-molded form. To avoid brittleness, the coal-digestion pitchshould not be too high-melting or be present in too small proportions.In other words, pliability is increased while retaining the non-flowingproperties of the mastic by increasing the amount of bituminousmaterials or fibers, or by using a bituminous material of lowersoftening point. Less pliable products are obtained by increasing theamount of filler, decreasing the amount of bituminous material, or byusing bituminous material of higher softening point. For some purposes,up to twenty-five percent by weight of heavy oil, above mentioned, isadvantageously added to the coal-digestion pitch prepared as described,for blending therewith.

More specifically, and by way of illustration, mastic sheets areprovided which are obtained by use of bituminous constituents withsoftening points in the range of about 75 C. to about 150 C., thoughcoal-digestion pitch with a softening point as low as 52 C. has beenused to advantage. A pliable mastic sheet that is nonbrittle at lowatmospheric temperatures and non-flowing at highest atmospherictemperatures has been provided by use of coal-digestion pitch of above90 C. softening point, and penetrations of not less than 10 at 32 F. andnot more than at 115 F. The stiffer mastic sheets have been providedwhich have been obtained by use of bituminous constituent with softeningpoint of at least C. and penetrations of 0 at 32 F., 0 to 5 at 77 F. and15 to 35 at 115 F. More pliable mastic sheets than the latter have beenobtained by the use of coal-digestion pitches with softening points ofas low as 52 C. and up to about 75 C. to 80 C. and with penetrations ofabove 10 at 32 F., above substantially 60 at 77 F., and of substantially230 to 240 and up to 300 at 115 F., all such sheets showing no tendencyto flow at 140 F.

Specifically, and for purposes of illustration, as to the proportions ofthe constituents of the mastic, the bituminous constituent varies fromabout 25 percent by weight to about 60 percent by weight (generallyabout 30 to about 50); the fibers are present to the extent of at leastabout 8 or 10 percent by weight; and the filler up to about 65 percentby weight, but generally of the order of 40 to 55 percent.

Examples of mastics employed in various sheet products including thoseillustrated in the accompanying drawings are as follows:

Example 1.140 parts by weight of coal-digestion pitch, such as thatprepared in Example A above, are melted in a rubber mill. parts byweight of dry clay are mixed with the molten coal digestion pitch, andfinally 40 parts by weight of fibers of the type recovered from rubberautomobile tires are incorporated. This forms a pliable mastic suitablefor extruding or molding shingles.

Example 2.-A pliable mastic composition suitable for roll roofing or forstrip shingles is made by mixing 52 parts by weight of coal-digestionpitch having a softening point of about 75 C. (ring and ball), with 40parts by weight of dry clay, finely divided slate dust, or other filler,on a rubber mill, or in a pug mill. and then incorporating 8 parts byweight of fiber, previously coated with tar. pitch or heavy oil. on arubber mill. or in a Banbury mixer.

Example 3.-A relatively stiff sheet mastic product suitable for use inpre-formed expansion joints, or insulation board, is prepared with thematerials set forth in Example 2 but in proportions of 50 parts ofcoal-digestion pitch, 36 parts of filler and 14 parts of fiber.

Example 4.-Sheets of semi-rigid character for use in sidings or panels,for various purposes and formed by milling at moderate temperatures, areprepared from mastic compounded from 325 parts by weight ofcoal-digestion pitch of about 75 C. softening point (ring and ball), 575parts by weight of slate dust, and parts by weight of fiber precoatedwith 15% by weight (based on the weight of fiber) of coal-digestionpitch, coal tar pitch or other pitch, tar, or high-boiling tardistillate.

Example 5.Pliable sheets are prepared from coaldigestion pitch, preparedin accordance with Example D above, by melting the pitch and mixing themolten pitch with clay and reclaimed tire fibers, in the proportion ofparts by weight of the pitch, 90 parts by weight of clay, and 40 partsby weight of fibers.

Example 6.One part by weight of coal tar heavy oil from coal tarobtained in high temperature carbonization of coal, and with a boilingpoint range above substantially 300 C. is mixed with 3 parts by weightof coal-digestion pitch prepared as in Example D. To 52% by weight ofthis mixture, are added 40% by weight of slate dust and 8% by weight ofreclaimed tire fibers, and mixing is completed on a rubber mill. A sheetis prepared from this mix which is strong and pliable.

Example 7.To three parts by weight of coal-digestion pitch prepared asin Example D. is added one part by weight of coal tar heavy oil fromcoal tar obtained in high temperature carbonization of coal, and toppedto substantially 300 C. To 50% by weight of this mix of pitch and oil,are added 36% by weight of slate dust and 14% by weight of reclaimedtire fibers. This mastic is rolled out into strong, pliable sheets.

Example 8.57.5% by weight of slate dust, and 10.0% by weight ofreclaimed tire fibers precoated with 1% coal-tar heavy oil are mixed ona rubber mill with 32.5% by weight of a mixture of three parts by weightof coaldigestion pitch prepared as in Example D, and one part by weightof coal tar heavy oil from coal tar obtained in high temperaturecarbonization of coal, and topped to substantially 300 C. The mix isrolled out into strong, pliable sheets.

By way of further examples, which may be designated as Examples 9, and11, in accordance with the above Examples 6, 7 and 8 respectively,strong pliable sheets are prepared from each of the mixes ofconstituents in the proportions stated in each of the latter examplesbut substituting for the coal-digestion pitch and heavy oil mixture, amixture of 85 parts by weight of said coaldigestion pitch and parts byweight of coal tar heavy oil from coal tar obtained in low temperaturecarbonization of coal, and topped to substantially 300 C.

Sheets are prepared in the aforegoing examples, which exhibit notendency to flow at temperatures up to 140 F. and above, and thereforeabove highest recorded summer atmospheric temperatures, even in verticalposition. Granules applied to a sheet as heretofore indicated, remain intheir position as originally placed, because of absence of plastic flowin the material of the sheet surface.

For certain purposes, the mastic in sheet material is alternativelyprepared from asphalt of about 100 C. (or above) softening point, orfrom coal tar pitch or other pitches of high softening points (120 to140 C.) mixed with to 40% heavy oil such as heavy Water gas tar heavyoil or other oil of high aromaticity and with a Y boiling point aboveabout 300 C. These bituminous substances are mixed with the desiredproportions of filler and fiber (preferably precoated). A mastic sheetprepared from the resulting compounded material is preferablysurface-treated as described below, with coaldigestion pitch,particularly of the type described in Examples A and D.

If a bituminous cement or dip-coat are employed to hold the granules onthe mastic, as shown in Fig. 4, it is preferred that the bituminous basethereof be a coaldigestion pitch. Alternatively, pigmented bituminouspaints or metal paints such as aluminum or bronze paints containing abituminous vehicle may be applied for heat and light reflectivepurposes, as in Fig. 3.

The article to be dip-coated is submerged in the molten pitch having aconsistency appropriate for forming a relatively thin coating onwithdrawal. If the pitch has a higher melting point than the meltingpoint of the bitumen in the mastic the time for submergence is less thanthat for coating with pitch of a lower melting point. The time may belong enough to permit some penetration which, if desired may also beobtained by applying pressure. The withdrawal of an article,particularly sheets or panels of large dimensions is preferably at adecelerating rate to obtain a uniform coating or a coating of uniformthickness throughout the area of a sheet. The total time of submergenceof the lowermost portions of a sheet should not be such as to result inany substantially different change in physical or structural conditionof the lowermost portion from that of the uppermost portion, as furtherindicated hereinbelow.

In preparing the above-mentioned bituminous cement in a preferred mannerfor cold application, a low-boiling solvent, such as coal tar naphtha,is added slowly at room temperature to molten coal-digestion pitch withagitation. The agitation is continued until all the solvent has beenintroduced, and the temperature of the final mixture has dropped to asubstantial extent below the boiling point of the solvent.

Solvent naphtha in the above procedure may in whole or in part bereplaced by other low-boiling coal tar solvents; fractions of heavywater gas tar and of light water gas tar distillates; and petroleumdistillates of high aromaticity or containing a preponderatingproportion of aromatics. The boiling point ranges of these solvents maybe from about C., or C., or from C. to about 200 C., depending upon thedrying properties desired. The boiling points may also range higher than200 C., as shown in the following table, depending upon the use of thecement:

Distillation of typical solvents Sample Source r Coal Tar Coal 'Iar ffgggy. G.

a 0. C, Q C c C The relative rate of evaporation of solvent andconsequent setting-up time of the adhesive at atmospheric temperaturesmay be changed as desired by proper choice of an aromatic solvent orsolvent fraction.

If relatively quick-drying adhesives are desired, the lower boilingsolvents of any of the sources mentioned may be selected for use, but ifslower setting cements are required the higher boiling fractions areselected for incorporation in the cement. In the above table, solvents(1) and (2) provide a relatively quick-drying cement; (3) provides aslightly slower drying cement; and (4) a considerably slower dryingcement.

Coal tar solvent naphtha, when employed in the cement, is prepared fromcoal tar distillate from which most of the tar acids, and in someinstances the tar bases, have been removed. Material boiling below 100C. is preferably removed to prevent too rapid setting of the cement uponapplication, and to minimize fire hazards arising from too low boilingdistillates if present. Coal tar solvents and solvents of higharomaticity are particularly compatible with coal-digestion pitches andprevent undesirable sludging and separation of different ingredientsinto layers.

The proportion of these solvents to be used in the cement depends uponthe desired consistency of the product. A relatively viscous product,suitable preferably for warm Weather or warm climate use, and better fordaubing, rather than brush application, is made from a mix ofapproximately 80% by weight of coal-digestion pitch (softening pointabout 75 C. to about 125 C.), and 20% by weight of a selected solvent. Amore fluid product, suitable for easy application in warm weather orwarm climates is made with about 75% by weight of such coal-digestionpitch and 25% by weight of a selected solvent. A product fluid enough(specific Engler viscosity, 50 cc. at 50 C., of approximately 18) forconvenient application at low to moderate temperatures is made withabout 70% by weight of such coal-digestion pitch and 30% by weight of aselected solvent.

A very fluid cement for brush or spray application is made with 60 partsby weight of coal-digestion pitch (softening point about 75 C. to about125 C.) and about 40 parts by weight of a selected solvent (boilingrange 100 C. to 200 C.). The specific Engler viscosity of such a cementis approximately 5 (50 cc. at 50 C.).

A fluid cement generally suitable for brush or spray application topitch coated articles, is made by cutting back 60 parts to 55 parts byweight of molten coal-digestion pitch of relatively high melting pointwith 40 to 45 parts by weight of aromatic solvent (boiling range about100 to 200 C.), thus producing an adhesive, quick drymg bituminouscement, that is applied cold, and having an Engler specific viscosity ofapproximately 8 to 15 (50 cc. at 25 C.).

Fillers, such as, slate dust or flour, finely divided talc or clay maybe added to the cement, if desired, to the extent of 25 to 30%, or evenup to 35% to provide a desired Weather-resistant adhesive.

The coal-digestion pitch in the cement is a coal-digestion pitch of thetypes specifically described above. If the pitch in a mastic surface hasthe composition of the coaldigestion pitch described in Example A above,it is preferred to use this pitch in the cement or dip coating sincebetter bonding is obtained than in cases where the compositions aredifferent. The same is true in the case of the coal-digestion pitchesdescribed in the other examples. Advantageous results are obtainedhowever by using a coal-digestion pitch in the cement or as dip-coatings6 (Fig. 4) prepared with constituents of any one of the tars or pitchesmentioned and by using for the preparation of sheets a mastic preparedwith constituents of any one of the other tars or pitches not used inthe coal-digestion pitch selected for said coatings, but the physicalcharacteristics (softening point, penetration etc.) of thecoal-digestion pitches employed should preferably be substantiallysimilar. For instance, in such combinations an effective bond isobtained by employing a heavy water gas tar-heavy water gas tar heavyoil-coal-digestion pitch in the mastic and a coal tar-heavy water gastar heavy oil-coal-digestion pitch as the dip-coating or in the cement,or vice versa; or a light water gas tar-light water gas tar heavyoil-coal-digestion pitch in the mastic and a heavy Water gas tar-heavywater gas tar heavy oil-coal-digestion pitch as the dip-coating materialor in the cement, or vice versa; and so forth.

Though a dip-coat treatment alone provides for superiorweather-resistance of a mastic article, it may be omitted as illustratedin Figs. 1 and 2 particularly if the fibers in the mastic have beenprecoated as indicated above.

Mastic compositions prepared from bituminous materials of inferiorweather-resistance or having less desirable rheological properties thanimproved mastics prepared with coal-digestion pitch, may be considerablyimproved by surface treatment by hot-dipping sheets and articles such asshingles, panels and others, in molten batches of the above-exemplifiedcoal-digestion pitches, or by application of compositions such as theabove cements prepared with selected solvents. Only a thin coating ofthe above-described coal-digestion pitch, as at 8 in Fig. 7, is neededon the conventional asphaltic or tar or pitch or other bituminous masticmaterial 9, to provide structural materials having superiorweather-resistant and rheological properties over wide temperatureranges. These properties are improved by increase of depth ofpenetration of the coating material toward the interior. Thecoal-digestion pitch of the type set forth in Example A is of particularvalue for this purpose. The coal-digestion pitches prepared as inExamples B, C, and D are also advantageously so applied, with or withoutblended heavy oil in the proportions set forth.

By way of further detail, the hot-dip surface treatment includes raisinga submerged sheet while in substantially vertical position in the bodyof the liquid coal-digestion pitch. While so raising the sheet in thepitch the rate of movement of the sheet in the bath is preferablyuniformly decelerated to provide the uniform application of the pitch.Since the sheet may normally be subject to change of shape whilesubmerged, the total time of submergence must not be such as to causedeformation or a change in the physical make-up of the sheet by contactwith the hot bath.

This surface treatment may be applied to mastic sheets of the presentinvention as well as to conventional bituminous mastic sheets, so as toobtain a mastic sheet having a uniformly high concentration ofcoal-digestion pitch of improved characteristics in at least theserviceexposed surfaces. While this serves to prevent surfacecracking inthe sheet on sudden bending or from mechanical shock, particularly inthe conventional bituminous mastic sheet, the treatment is not entirelynecessary for sheets made from mastics of the aforegoing examples sincethe coal-digestion pitch is already present throughout the body of suchsheets as in Figs. 1 and 5, for in stance.

The improved mastic has many advantages particularly in constructionaluse as siding and roofing. Strength in a finished molded product isobtained by application of moderate heat and pressure upon the mastic tobe shaped and with a minimization of metal consumption. The sheet, assuch, can be attached to surfaces and ap plied in a manner wellunderstood in the various arts. In adapting the sheet to particularuses, it can be included in plural-ply sheets or attached to webs orlayers of other material to suit requirements. In the shaping ofarticles made of the mastic, molding temperatures and pressures areemployed, for instance, respectively of about 75 C. to about 150 C.depending upon the melting point of the binder, and of from about 200lbs. per sq. in. to about 2000 lbs. per sq. in. depending upon thethickness of a sheet and amount of compression required. Sticking of themastic to molding faces is minimized by applying simply a thin film of alubricating oil or grease preferably of petroleum origin to the moldsurfaces, or by applying a light covering of finely divided mineralaggregate such as ground talc or slate dust or stone dust or the like,or by simultaneous use of both of these treatments.

The improved mastic herein described serves not only as heat insulation,but also as sound and electrical insulation. Its unique water-repellingproperties are clearly shown by comparison with conventional mastics.After immersing the improved mastic in water for ten days at roomtemperature and also at 50 C., a change in weight of only 1% is noted;whereas other commercially known bituminous mastics submitted to similartests show increases in weight of 15% to 25%.

The present application is a continuation-in-part of application SerialNo. 508,856, filed November 3, 1943, now abandoned.

What is claimed is:

1. An article of manufacture consisting of an improved coherent,self-sustaining, prefabricated, flexible, bituminous mastic sheet thatis non-brittle and non-flowing at atmospheric temperatures and that iscomposed of about 25 percent to about 60 percent by weight ofcoal-digestion pitch, at least about 8 percent by weight of discretefiber particles and up to about 65 percent by weight of inert,finely-divided, granular filler, the said coal-digestion pitch in atleast the service-exposed surfaces of the said sheet containing coalthermally digested and dispersed in heat liquefiable bitumen and havingblended therewith as an essential ingredient heavy hydrocarbon oilhaving a preponderating proportion of aromatics, and the saidcoaldigestion pitch having in combination a softening point above C., apenetration of 32 F. of not less than 10 with 200 grams for 60 seconds,and a penetration at F. of not more than 70 with 50 grams for 5 seconds,for preventing surface-cracking in said sheet on sudden bending and frommechanical shock.

2. An article of manufacture consisting of an improved, coherent,self-sustaining, pre-fabricated, flexible, bituminous mastic sheet thatis non-brittle and non-flowing at atmospheric temperatures and that iscomposed of about 25 percent to about 60 percent by weight ofcoal-digestion pitch, at least about 8 percent by weight of discretefiber particles and up to about 65 percent by weight of inert, finelydivided, granular filler, the said pitch containing in at least theservice-exposed surfaces of the sheet thermally digested coal inheat-liquefiable bitumen and blended with heavy water gas tar heavy oil,and said coal-digestion pitch having in combination a softening pointabove 90 C., a penetration at 32 F. of not less than 10 with 200 gramsfor 60 seconds. and a penetration at 115 F. of not more than 70 with 50grams for 5 seconds, for preventing surface-cracking in said sheet onsudden bending and from mechanical shock.

3. An article of manufacture consisting of an improved, coherent,self-sustaining, pre-fabricated, flexible, bituminous mastic sheet thatis non-brittle and nonflowing at atmospheric temperatures and that iscomposed of about 25 percent to about 60 percent by weight ofcoal-digestion pitch, at least about 8 percent by weight of discretefiber particles and up to about 65 percent by weight of inert, finelydivided, granular filler, the said pitch containing in at least theservice-exposed surfaces of the sheet thermally digested coal inheatliquefiable bitumen and blended with light water gas tar heavy oil,and said coal-digestion pitch having in combination a softening pointabove 90 C., a penetration at 32 F. of not less than 10 with 200 gramsfor 60 seconds, and a penetration at 115 F. of not more than 70 with 50grams for seconds, for preventing surface-cracking in said sheet onsudden bending and from mechanical shock.

4. An article of manufacture consisting of an improved, coherent,self-sustaining, pre-i'abricated, flexible, bituminous mastic sheet thatis non-brittle and non-flowing at atmospheric temperatures and that iscomposed of about 25 percent to about 60 percent by weight ofcoal-digestion pitch, at least about 8 percent by weight of discretefiber particles and up to about 65 percent by weight of inert, finelydivided, granular filler, the said pitch containing in at least theservice-exposed surfaces of the sheet thermally digested coal inheat-liquefiable bitumen and blended with coal tar heavy oil, and saidcoal-digestion pitch having in combination a softening point above 90C., a penetration at 32 F. of not less than 10 with 200 grams for 60seconds, and a penetration at 115 F. of not more than 70 with 50 gramsfor 5 seconds, for preventing surface-cracking in said sheet on suddenbending and from mechanical shock.

5. An article of manufacture consisting of an improved, coherent,self-sustaining, pre-fabricated, flexible, bituminous mastic sheet thatis non-brittle and non-flowing at atmospheric temperatures and that iscomposed of about 25 percent to about 60 percent by weight ofcoal-digestion pitch, at least about 8 percent by weight of discretefiber particles and up to about 65 percent by weight of inert, finelydivided, granular filler, the said pitch containing in at least theservice-exposed surfaces of the sheet thermally digested coal inheat-liquefiable bitumen and blended with an oil selected from a groupconsisting of heavy water gas tar heavy oil, light water gas tar heavyoil, and coal tar heavy oil, and said coal-digestion pitch having incombination a softening point above 90 C., a penetration at 32 F. of notless than 10 with 200 grams for 60 seconds, and a penetration at 115 F.of not more 35 2,550,681

than 70 with grams for 5 seconds, for preventing surface-cracking insaid sheet on sudden bending and from mechanical shock.

6. An article of manufacture consisting of an improved, coherent,self-sustaining, pre-fabricated, flexible, bituminous mastic sheethaving at least in its service-exposed surfaces a uniformly highconcentration of coal-digestion pitch non-flowing in said surfaces invertical position at highest atmospheric temperatures and for preventingsurface-cracking in said sheet on sudden bending or from mechanicalshock.

7. An article of manufacture consisting of an improved, coherent,self-sustaining, pre-fabricated, flexible, bituminous mastic sheet thatis non-flowing at temperatures up to 140 F. and that is composed ofabout 25 percent to about percent by weight of coal-digestion pitch, atleast about 8 percent by weight of discrete fiber particles and up toabout percent by weight of inert, finely-divided, granular filler, thesaid coal-digestion pitch containing coal thermally digested anddispersed in heat-liquefiable bitumen and having blended therewith heavyhydrocarbon oil having a preponderating proportion of aromatics.

References Cited in the file of this patent UNITED STATES PATENTS278,481 Allen May 29, 1883 980,664 Murphy Jan. 3, 1911 1,300,550 BakerApr. 15, 1919 2,354,593 Greider et al July 25, 1944 2,395,041 Fair Feb.19, 1946 2,396,690 Fair Mar. 19, 1946 2,455,923 Fair Dec. 14, 19482,472,100 Fair June 7, 1949 Fair May 1, 1951

6. AN ARTICLE OF MANUFACTURE CONSISTING OF AN IMPROVED, COHERENT,SELF-SUSTAINING, PRE-FABRICATED, FLEXIBLE, BITUMINOUS MASTIC SHEETHAVING AT LEAST IN ITS SERVICE-EXPOSED SURFACES A UNIFORMLY HIGHCONCENTRATION OF COAL-DIGESTION PITCH NON-FLOWING IN SAID SURFACES INVERTICAL POSITION AT HIGHEST ATMOSPHERIC TEMPERATURES AND FOR PREVENTINGSURFACE-CRACKING IN SAID SHEET ON SUDDEN BENDING OF FROM MECHANICALSHOCK.